"meretricious ornamentation..."See in text(The Gift of the Magi)
Meretricious means aesthetically attractive, but containing no actual value. In this case, Della hopes that the watch will be valuable because of its sensible use, not its flashiness. This is also a piece of dramatic irony. The love between the couple is far more valuable to both of them than any material goods. Therefore the idea of purchasing a material gift in the hope that it will make Jim happy is itself “meretricious ornamentation.”
The mendicancy squad were police forces who arrested homeless people and beggars. This phrase tells the reader that the conditions this couple are living in are near the poverty level.
"beggar description..."See in text(The Gift of the Magi)
“Beggar description” is an outdated term that means unable to be described. In this case, O. Henry is explaining to the reader that the apartment is not so horrible that it can’t be lived in; however, it’s not so lovely as to deserve a lengthy description. Because this is a Christmas Tale, a lot of the imagery is left to the imagination of the reader.